YORK HIGH EFF TROUBLESHOOTING

[harshal]

WAS ON SERVICE CALL ON YORK HIGH EFF FURNACE.IT WOULD NOT IGNITE WITH THE BURNER DOOR ON.IF I REMOVE THE BURNER DOOR IT WOULD IGNITE AND RUN NORMALLY.ITS TWO PIPE ATTCHED TO IT.ONE FOR COMBUSTION AIR AND ANOTHER ONE FOR THE FLUE GAS.I FOUND NO BLOCAKGE ON AIR INTKE AS WELL/I THOUGH IT WOULD BE BURNER SO I WASHED THE BURNER N PUT IT BACK.BUT IT STILL WOULD NOT MAKE ANY DIFFERENCE.ANY THOUGHTS WHAT COULD BE THE PROBLEM?

[Admin]

Is it a P2U or P3U York model?

With the burner door on the ignitor glows and gas flows and doesn't ignite?  Or does the ignitor not glow possibly due to pressure switch not closing?

I would cut the intake pipe and try it with the burner door on to make sure it's not an intake problem but if you're sure the intake is fine I would be looking at the heat exchangers.

Is the furnace blower running continuously or is it off when the burners are trying to light?

Allow the burners to run for a few minutes to stabilize and wait until the blower starts then use a combustion analyser to verify your readings.  You want to test the flue gas inside the exhaust vent as close as possible to the furnace.

The excess air should be above 30%.  For a sealed combustion high efficiency furnace a normal O2 reading would be around 7% and a normal CO2 reading would be around 5.8%.

A cracked heat exchanger could raise the O2 and lower the CO2 readings.  I have found alot of cracks on the primary heat exchangers of York furnaces.

[harshal]

York.M- P2URD12N07501A.
With or without the burner door,the gas would go through the burner area.However with the door on it wouldn't ignite,igniter would light and gas would flow through the gas valve though
.If I remove the burner door it would ignite.
Also I cut the air intake to see if any blockage.found none.
I don't have the CO analyzer,so can't try that test.
Where and how u found the crack on this heat exchanger?

[Admin]

Have a look at the picture below.  TSP = Temperature Stress Point.

You should be able to cut a inspection hole in the supply plenum.  Have a look at the top of the primary cells using a scope or inspection mirror.

Is the indoor blower fan running while the burners try to light?  Make sure the fan is set to "AUTO" and see if the burners will light.  That would be a good indicator a crack is causing the problem.